API to discover granted Uri permissions.

Now that granted Uri permissions can be persisted across reboots,
offer APIs to discover them. Returns incoming or outgoing grants
matching the requested flags and mask. Add helper method to discover
"open" documents using this new API and filtering for non-documents.

Require that callers own at least of the filtering packages to avoid
exposing all grants. Switch internal grant tracking to use ArrayMap.

Change-Id: I0a755f221d0d160b411f8d3cfc48279b64345733